IO Error: HTTP resource not retrievable. The HTTP status from the remote server was: 401

I'm getting:

 1.

    *IO Error*: HTTP resource not retrievable. The HTTP status from the
    remote server was: 401.

The webpage being tested is protected by username/password that I've 
entered. I've used the validator 1-2 weeks ago on the same domain 
without any problem.

Any suggestions?

Is this a version (Version: 15.7.26) issue?

Thanks!